Push-pull magnetoresistive sensors are widely used in design because of the high sensitivity signal and temperature compensation performance Often, a flip die method is used to obtain push magnetoresistive sensing units and pull magnetoresistive sensing units. For a single-axis magnetoresistive sensor such as an X-axis magnetoresistive sensor, at least two die are needed, and the rotation angle of the dice needs to be flipped for 0 and 180 degrees respectively. For a two-axis magnetoresistive sensor such as two-axis X-Y magnetoresistive sensor, at least four dice are needed, and the rotation angles of the dice need to be 0, 90, 180 and 270 degrees respectively. The disadvantages are that many dice are needed, the angular alignment of the dice is performed by mechanical operations, and therefore there is an angle error that degrades sensor performance. Moreover, the dice of the sensor need to be connected through leads, increasing the complexity of the process.
Another solution is to use soft ferromagnetic flux concentrators to construct a specific magnetic path on a magnetoresistive sensing unit string in order to steer the direction of the X-direction external magnetic field into the X-direction and the −X-directions after passing through soft ferromagnetic flux concentrators. That is, the preparation of the push-pull magnetoresistive sensor is realized by altering the magnetic field direction in the vicinity of the multilayer film structure, while leaving the sensingdirection of the magnetoresistive sensor film unchanged. The disadvantages of this method are that the introduction of the soft ferromagnetic flux concentrator increases the complexity of the process, and moreover, the linearity of the magnetoresistive sensor may be affected due to the hysteresis caused by the magnetic domain movement within the soft ferromagnetic flux concentrators.
Additionally, from the point of view of statistical averaging, for X and −X magnetoresistive sensing units, the magnetoresistive sensing units having the have orientation angles of 0 degrees and 180 degrees, but manufacturing tolerances produce a distribution of angles about the 0 and 180 degree directions. For Y and −Y magnetoresistive sensing units, the magnetoresistive sensing units have orientation angles of 90 degrees and 270 degrees, with many magnetoresistive sensing units have a distribution within a certain range taking 90 degrees and 270 degrees as centers. The orientation angle range usually varies in the range of −90 to +90 degrees. Therefore, for the double-axis X-Y linear or angular sensors, it is not easy to accurately measure the magnetic field in the range of 0 to 360 degrees without some error caused by inaccurate die placement.
In the laser scanning method, the multilayer film structures of the magnetoresistive sensing units, the magnetoresistive sensing units such as TMR or GMR spin-valve magnetoresistive sensing units are heated to a temperature above the blocking temperature of the antiferromagnetic layer by scanning a laser, and applying an external magnetic field in the direction of X or −X, Y or −Y as well as the direction at a (−90,+90) extended angle is applied along a particular direction in the cooling process, and thus push-pull single-axis or double-axis magnetoresistive sensors can also be produced, so that the magnetization direction of the antiferromagnetic layer can be changed by laser thermal annealing without changing the multilayer film structure of the sensor, and the problems of die alignment and addition of the soft ferromagnetic flux concentrator are avoided. However, there are a great number of magnetoresistive sensing units on a wafer during production. How to select a suitable layout design of magnetoresistive sensing units with various magnetic moment orientations of single-axis or double-axis magnetoresistive sensors and select a suitable laser scanning path to improve the efficiency of laser writing process is a problem to be solved by the present invention.